1. Field of the Invention
The present invention relates to a method and an apparatus for manufacturing a thin film used, for example, for electronic components. The present invention also relates to a product of layered thin films and an electronic component using the same.
2. Description of the Prior Art
In our modern society, thin films play a role in various fields, and are used, for example, in wrapping paper, magnetic tapes, capacitors, semiconductors and other everyday products.
Without such thin films, the fundamental trends of technology in recent years, which are higher performance and miniaturization, would not have been possible. At the same time, there have been various developments with regard to methods for forming thin films to satisfy industrial needs, for example, towards continuous vacuum vapor deposition while winding that is useful for high-speed mass production, and which can be applied to wrapping paper, magnetic tapes, capacitors, etc.
A thin film with the desired characteristics can be formed by selecting the evaporation material and the substrate material in accordance with the purpose of the thin film to be formed, and forming a thin film while a potential is applied to the substrate, while introducing a reactive gas into a vacuum if necessary. For example, an oblong magnetic recording medium can be obtained by using an evaporation material including a magnetic element such as Co, Ni, or Fe to manufacture the magnetic recording medium, and performing reactive vapor deposition while introducing an oxide gas into the vacuum container.
Moreover, on semiconductors, thin films are mainly formed by sputtering. Sputtering is also particularly useful for the formation of thin films using materials based on ceramics, and often ceramic thin films with several .mu.m or more thickness are formed by coating and firing, and those of 1 .mu.m or less thickness are formed by sputtering.
On the other hand, methods based on coating with paint are used to form thin films using resin materials, and reverse coating and die coating are used industrially, and it is common to dry and harden the material, which has been diluted with a solvent, after the coating step. Moreover, the lower limit of the film thickness for resin films formed with these processes depends on the used material. Often, the film thickness is about 1 .mu.m, and often film thicknesses below that are difficult to obtain.
In usual coating means, dilution with a solvent is necessary for the formation of ultra-thin resins films in order to achieve a thickness of the coating directly after the coating that is at least several .mu.m thick, but often it is not possible to obtain resin thin films of 1 .mu.m or less. Moreover, when dilution is performed with a solvent, defects occur easily in the coating film after the coating, and it is further not preferable with regard to environmental protection.
Therefore, there is a need for a method with which a resin thin film can be formed without dilution with a solvent, and for a method with which ultra-thin resin thin films can be obtained reliably. As a method solving these problems, it has been proposed to form a resin thin film in a vacuum.
In this method, a resin material is vaporized in a vacuum, and then adhered to a supporting base. With this method, a resin film without void defects can be formed, and dilution with a solvent is not necessary.
By depositing thin films of a different kind on a ceramic thin film or on a resin thin film, several composite thin films that could not be obtained conventionally can be obtained, and the fields for their industrial application are extremely diverse. Among these, chip-shaped electronic parts are in high demand, and capacitors, coils, resistors, capacitive batteries and components that are combinations of these can be formed in extremely small sizes and with high performance by layering thin films, and are already included in products and their market expansion has begun.
Needless to say, electrodes are indispensable for obtaining electronic components, but in electronic components using metal thin films, metal thin films with different potentials can be formed in an electronic component by subjecting the metal thin films to patterning. This means that an electronic component can be formed by using pattern portions as insulating regions to divide a metal thin film into a plurality of metal thin films, and layering such layers alternately with insulating thins films.
Electronic components with multi-layers of patterned metal thin films and insulating thin films can be formed with the apparatus outlined in FIG. 2. In FIG. 2, a source 8 for forming a metal thin film, a source 9 for forming an insulating thin film, a curing apparatus 10, and an apparatus 11 for applying patterning material are arranged around a can 7 for supporting a layered film. The can 7 rotates with constant velocity in the arrow direction and a product of layered thin films is formed on the peripheral surface of the can 7, having a number of thin films that corresponds to the number of rotations of the can 7. These are arranged inside a vacuum container 5, whose interior is maintained at a vacuum or at low pressure with an evacuation system 6 including, for example, a vacuum pump.
For the source 8 for forming a metal thin film, a resistance-heating vapor source, an inductance-heating vapor source, an electron beam vapor source, a sputtering vapor source, a cluster vapor source, or any other device used for forming a thin film or any combination thereof can be used, in accordance with the metal thin film to be formed.
For the source 9 for forming an insulating thin film, an apparatus for vaporization by heating with a heater or vaporization or atomization with ultrasonic waves or spraying a resinous material, or sputtering a ceramic-based material, or sputtering, vapor deposition etc. of an oxide can be used, in accordance with the insulating thin film to be formed.
The curing apparatus 10 cures the insulating thin film formed with the source 9 for forming an insulating thin film to a predetermined hardness. For the curing apparatus 10, UV curing, electron curing, heat curing, or a combination thereof can be used if a resin thin film is used for the dielectric.
As a method for obtaining a patterned metal thin film, there is an approach called "oil margin". This involves forming a metal thin film by vapor deposition or the like after thinly applying a thin patterning material, and using the fact that the metal thin film is not formed on the patterning material. A method that can be used for applying patterning material in a vacuum is heating a patterning material that is enclosed in a nozzle having micro-aperture portions (nozzle holes) in accordance with the pattern, and spraying a vapor of that material from the nozzle holes, which condenses on the surface where a metal thin film is to be formed.
For the patterning material, an oil, or any other material that is suitable for patterning a metal thin film can be used. The thusly formed metal thin film is formed at all portions except where the patterning had been formed, so that it is possible to form a metal thin film having the desired pattern.
FIG. 3 is an example of the structure of a metal thin film formed on the peripheral surface of the can 7. FIG. 3 shows a partial development along the peripheral surface of the can 7. The arrow 70 in this drawing indicates the travel direction of the peripheral surface of the can 7. In the example in FIG. 3, several band-shaped metal thin films 1 that are divided by the pattern positions 4 are formed on the peripheral surface of the can.
With the apparatus in FIG. 2, a product of layered thin films is obtained on the peripheral surface of a can 7 by alternately layering a metal thin film patterned as shown in FIG. 3 and an insulating thin film on the peripheral surface of the can 7. Next, this layered product is cut in the layering direction. The relation between the pattern position and the cutting position is set appropriately. Then, an electronic component can be manufactured by forming electrodes by thermal spraying or the like if necessary.
FIG. 4 is a cross-sectional view showing an outline of the internal structure of an electronic component that can be used as a capacitor. In the electronic component in FIG. 4, an insulating thin film 2 and a metal thin film 1 are layered alternately and each metal thin film 1 is divided into two at the pattern position 4. In the electronic component in FIG. 4, the pattern position 4 of each metal thin film differs from the pattern position 4 of the next metal thin film above or below, and matches the pattern position 4 of the metal thin film after that. With the apparatus in FIG. 2, this can be realized by shifting the patterning position back and forth for a predetermined distance parallel to the rotation axis of the can 7 once for each rotation of the can 7. In the electronic component in FIG. 4, electrodes 3 are formed on two opposing side surfaces of a layered product as described above, which are electrically connected to the metal thin films 1. Thus, the electronic component in FIG. 4 functions as a capacitor with the insulating thin films 2 as the dielectric.
To perform the patterning with oil margins with great accuracy, the patterning material has to be applied very precisely. Examples for parameters that influence the pattern width are the properties of the patterning material, the nozzle temperature, the gap between the nozzle holes and the supporting base to which the patterning material is applied, and the size of the nozzle holes. Especially if marks due to contact between the nozzles and the supporting base cause problems, it is necessary to keep a small gap between the nozzles and the supporting base. The pattern width becomes larger, the larger the nozzle holes are and the larger the gap between the nozzle holes and the supporting base is, but if the pattern width is increased like this, the edges of the pattern become blurry. Therefore, there is a need for a patterning method wherein the edges do not blur, even when the pattern width becomes large.